WO 2007/149934 A2 describes an optical method and apparatus for measuring properties of a travel vehicle or a travel surface upon which the vehicle travels, which method includes providing an incident light from a light source to the travel surface, collecting light reflected from the travel surface, determining a surface-induced Doppler shift from the incident and collected light and determining at least one of a motion property of the travel vehicle and a surface property of the travel surface based on the determined surface-induced Doppler shift. The apparatus is bulky and is impractical for many travel vehicles.